| /* |
| * This file is part of the Jikes RVM project (http://jikesrvm.org). |
| * |
| * This file is licensed to You under the Eclipse Public License (EPL); |
| * You may not use this file except in compliance with the License. You |
| * may obtain a copy of the License at |
| * |
| * http://www.opensource.org/licenses/eclipse-1.0.php |
| * |
| * See the COPYRIGHT.txt file distributed with this work for information |
| * regarding copyright ownership. |
| */ |
| package org.mmtk.policy; |
| |
| import org.mmtk.plan.TransitiveClosure; |
| import org.mmtk.utility.heap.FreeListPageResource; |
| import org.mmtk.utility.heap.VMRequest; |
| import org.mmtk.utility.DoublyLinkedList; |
| |
| import org.mmtk.vm.VM; |
| |
| import org.vmmagic.pragma.*; |
| import org.vmmagic.unboxed.*; |
| |
| /** |
| * Each instance of this class corresponds to one explicitly managed |
| * large object space. |
| */ |
| @Uninterruptible |
| public final class ExplicitLargeObjectSpace extends BaseLargeObjectSpace { |
| |
| /**************************************************************************** |
| * |
| * Instance variables |
| */ |
| private final DoublyLinkedList cells; |
| |
| /**************************************************************************** |
| * |
| * Initialization |
| */ |
| |
| /** |
| * The caller specifies the region of virtual memory to be used for |
| * this space. If this region conflicts with an existing space, |
| * then the constructor will fail. |
| * |
| * @param name The name of this space (used when printing error messages etc) |
| * @param pageBudget The number of pages this space may consume |
| * before consulting the plan |
| * @param vmRequest An object describing the virtual memory requested. |
| */ |
| public ExplicitLargeObjectSpace(String name, int pageBudget, VMRequest vmRequest) { |
| super(name, pageBudget, vmRequest); |
| cells = new DoublyLinkedList(LOG_BYTES_IN_PAGE, true); |
| } |
| |
| |
| /**************************************************************************** |
| * |
| * Collection |
| */ |
| |
| /** |
| * Prepare for a new collection increment. |
| */ |
| public void prepare() { |
| } |
| |
| /** |
| * A new collection increment has completed. |
| */ |
| public void release() { |
| } |
| |
| /** |
| * Release a group of pages that were allocated together. |
| * |
| * @param first The first page in the group of pages that were |
| * allocated together. |
| */ |
| @Inline |
| public void release(Address first) { |
| ((FreeListPageResource) pr).releasePages(first); |
| } |
| |
| /** |
| * Perform any required initialization of the GC portion of the header. |
| * |
| * @param object the object ref to the storage to be initialized |
| * @param alloc is this initialization occuring due to (initial) allocation |
| * (true) or due to copying (false)? |
| */ |
| @Inline |
| public void initializeHeader(ObjectReference object, boolean alloc) { |
| Address cell = VM.objectModel.objectStartRef(object); |
| cells.add(DoublyLinkedList.midPayloadToNode(cell)); |
| } |
| |
| /**************************************************************************** |
| * |
| * Object processing and tracing |
| */ |
| |
| /** |
| * Trace a reference to an object under a mark sweep collection |
| * policy. If the object header is not already marked, mark the |
| * object in either the bitmap or by moving it off the treadmill, |
| * and enqueue the object for subsequent processing. The object is |
| * marked as (an atomic) side-effect of checking whether already |
| * marked. |
| * |
| * @param trace The trace being conducted. |
| * @param object The object to be traced. |
| * @return The object (there is no object forwarding in this |
| * collector, so we always return the same object: this could be a |
| * void method but for compliance to a more general interface). |
| */ |
| @Inline |
| public ObjectReference traceObject(TransitiveClosure trace, ObjectReference object) { |
| return object; |
| } |
| |
| /** |
| * @param object The object in question |
| * @return True if this object is known to be live (i.e. it is marked) |
| */ |
| @Inline |
| public boolean isLive(ObjectReference object) { |
| return true; |
| } |
| |
| /** |
| * Return the size of the per-superpage header required by this |
| * system. In this case it is just the underlying superpage header |
| * size. |
| * |
| * @return The size of the per-superpage header required by this |
| * system. |
| */ |
| @Inline |
| protected int superPageHeaderSize() { |
| return DoublyLinkedList.headerSize(); |
| } |
| |
| /** |
| * Return the size of the per-cell header for cells of a given class |
| * size. |
| * |
| * @return The size of the per-cell header for cells of a given class |
| * size. |
| */ |
| @Inline |
| protected int cellHeaderSize() { return 0; } |
| |
| /** |
| * Sweep through all the objects in this space. |
| * |
| * @param sweeper The sweeper callback to use. |
| */ |
| @Inline |
| public void sweep(Sweeper sweeper) { |
| Address cell = cells.getHead(); |
| while (!cell.isZero()) { |
| Address next = cells.getNext(cell); |
| ObjectReference obj = VM.objectModel.getObjectFromStartAddress(cell.plus(DoublyLinkedList.headerSize())); |
| if (sweeper.sweepLargeObject(obj)) { |
| free(obj); |
| } |
| cell = next; |
| } |
| } |
| |
| /** |
| * Free an object |
| * |
| * @param object The object to be freed. |
| */ |
| @Inline |
| public void free(ObjectReference object) { |
| Address cell = getSuperPage(VM.objectModel.refToAddress(object)); |
| cells.remove(cell); |
| release(cell); |
| } |
| |
| /** |
| * A callback used to perform sweeping of the large object space. |
| */ |
| @Uninterruptible |
| public abstract static class Sweeper { |
| public abstract boolean sweepLargeObject(ObjectReference object); |
| } |
| } |